Monolateral Pterional Keyhole Approaches to Bilateral Cerebral Aneurysms: Anatomy and Clinical Application

Abstract

Objective: To study the anatomy and clinical application of monolateral pterional keyhole approaches for treating bilateral cerebral aneurysms.

Methods: Twelve formalin-fixed cadaveric heads underwent right pterional keyhole approaches for management of simulative contralateral aneurysms. The length of the contralateral middle cerebral artery (MCA), distal internal carotid artery (DICA), anterior cerebral artery, and ophthalmic segment of the internal carotid artery (OICA) was recorded. The operability of contralateral aneurysms was assessed using a modified numeric grading system. A total of 16 patients (12 patients with ruptured aneurysms) with bilateral cerebral aneurysms undergoing contralateral pterional keyhole approaches were included.

Results: The contralateral A1 segment of the anterior cerebral artery, proximal A2 segment, M1 segment of the MCA, DICA, and OICA was exposed via pterional keyhole approaches. An additional 2 mm of the OICA was exposed after incision of the falciform dural fold was completed. Contralateral aneurysms of the M1 segment (posterior), M2 segment, MCA bifurcation (inferior), A2 segment (lateral), DICA (posterior and lateral), and OICA (superior, inferior, and lateral) could not be fully exposed to perform simulated surgical clipping (operability rate <75%). A total of 36 aneurysms underwent adequate surgical clipping via unilateral pterional keyhole approaches, whereas 1 aneurysm of the A3 segment did not.

Conclusions: Contralateral aneurysms of the M1 segment (anterior, superior, and inferior), MCA bifurcation (superior and lateral), A1 segment, A2 segment (anterior, posterior, and medial), internal carotid artery bifurcation, DICA (anterior and medial), and OICA (medial) were fully exposed from different angles and surgical maneuvers were performed via pterional keyhole approaches, including in patients presenting with subarachnoid hemorrhage.

Keywords: Anatomy; Bilateral cerebral aneurysms; Contralateral; Pterional keyhole approach.